NEW YORK -- Women's stagnant enrollment in M.B.A. programs will persist unless business schools and businesses become female-friendlier places and start wooing women at much younger ages.

So concludes a groundbreaking study, set for release Friday, based on a poll of 1,684 male and female M.B.A. graduates of 12 leading U.S. business schools between 1981 and 1995. The study seems sure to spark more joint efforts between those schools and the 13 big companies that sponsored the research, such as Chase Manhattan Corp.,...